Chapter 4 Atoms

Dalton's atomic theory was accepted because

• there was evidence to support it

• Democritus said that it was correct

• Dalton invented the electron microscope

• Dalton showed how molecules are formed

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Atoms have no electric charge because they

• have an equal number of charged and noncharged particles.

• have neutrons in their nuclei.

• have an equal number of electrons and protons.

• have an equal number of neutrons and protons.

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According to the new model of the atom, electrons behave like

• planets orbiting the sun.

• waves on a vibrating string.

• light energy in a vacuum.

• planets rotating on their axes.

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According to modern atomic theory, it is nearly impossible to determine an electron's exact

• color.

• position.

• charge.

• mass.

Valence electrons determine an atom's

• mass.

• chemical properties.

• electric charge.

• period.

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If the atomic mass of carbon is 12 u, 1 mole of pure carbon will have a mass of

• 6 g.

• 6 mol.

• 12 g.

• 12 mol.

Democritus's original atomic theory was revised because it

• claimed matter is made of atoms.

• claimed atoms could be divided.

• explained what electrons are.

• did not have scientific basis.

A subatomic particle that has a negative charge is called a(n)

• molecule

• electron

• element

• compound

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Who determined that atoms could be divided?

• Democritus

• Thomson

• Dalton

• Rutherford

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Thomson made his discovery about the atom during an experiment using

• thermal energy.

• kinetic energy.

• cathode rays.

• X rays.